In patent application FR 2 754 893 the Applicant has already proposed a Sagnac effect gyroscope structure having a multimode optical fiber loop in which a dual phase-conjugate mirror is disposed. Light reaching said mirror from one side thereof constitutes a pumping wave for light reaching said mirror from the other side thereof, and vice versa.
Such an optical gyroscope structure makes it possible to achieve the same sensitivity both for fast phase shifts and for phase shifts that are slower.
In addition, it presents advantages in terms of cost, given that multimode fibers are less expensive than polarization-conserving monomode fibers of the kind generally used in Sagnac effect gyroscopes.
Nevertheless, multimode fibers are of large diameter which gives rise to gyroscope coils of large size, particularly when the length of fiber used is itself considerable.
Furthermore, mode decomposition, or speckle patterning, at the outlet from a multimode fiber turns out to be highly sensitive to variation in certain external parameters, such as temperature or vibration, which can give rise to local variations of index. This makes it necessary to isolate the coil from external stresses.